The invention relates to a magnetically operated electrical switch construction which is responsive to hydraulic flow, and in particular the invention is concerned with the single-direction or straight flow-through variety of such devices.
Many types of flow switches have been proposed and marketed within the past few years. Those units which incorporate flow-through capability have utilized a magnet-bearing piston in the flow stream; in some configurations the involved flow of hydraulic fluid is allowed to exit at a right angle to the direction of inlet flow, and in other configurations, the flow is either through or around the piston, in order that inlet and exit flows may be in the same direction. In the right-angle exit situation, the presence of a sufficient flow to actuate the device will displace the piston into a "bypass" location wherein there is at least some reduction in pressure drop across the unit. On the other hand, with the single-direction variety there has been no resulting reduction in pressure drop, however far the piston is displaced; this is because the piston remains in the fluid path, as a continuing restriction to flow through the unit.